The present invention is directed to a process of enhancing the bonding of polyester-based polymer concrete overlay to substrates to provide an improved overlay structure.
Polymer concrete compositions have been developed as surface materials to repair and renew pavements, bridge decks, parking decks, as well as warehouse and factory floors and the like. Such materials are also useful in enhancing the structure's surface by making it resistant to intrusion of water, petroleum products and other chemicals. Unlike conventional portland cement compositions, in polymer concretes the aggregate is held together by a polymer matrix.
Polymer concrete compositions are composed of aggregate mixed with a liquid organic compound (monomer) capable of forming a polymeric material upon casting at the jobsite. The composition may contain additional components, such as preformed polymeric material, colorants, shrink control agents, modifiers and the like. Two commonly used polymer concretes are acrylic concretes based on polymethylmethacrylate and the like and polyester concretes based on grafted polyesters.
Because of the relatively high cost of polymer concrete compositions, they are not a replacement for portland concrete. Instead, they are normally used as an overlay to repair and/or enhance conventional portland cement based concrete structures. Polymer concretes, because they do not contain or develop excessive amounts of water during cure, have few voids and, thereby, provide a dense impermeable overlay. The polymers used are required to be highly resistant to chemical attack such as acids, bases, oils, detergents and fats.
Polymer concrete overlays are normally from about 0.25 to 2 inches thick. Due to their hydrophobic nature, they do not form a strong bond with concrete substructures, especially if the substructure is damp or wet. To enhance the bond between the substrate and the overlay, a primer coating is conventionally applied to the substrate prior to application of the overlay polymer concrete composition. Conventionally, the primer is of a substantially similar composition to that of the overlay so as to be compatible with the overlay and capable of having the overlay at least partially dissolve the primer, thereby enhancing adhesion. For example, acrylic based primers are conventionally used with acrylate and methacrylate polymer concretes. Urethane and styrene based primers are conventionally used with styrene-grafted polyester polymer concrete compositions.
In contrast to polymer concrete compositions, high molecular weight methacrylate monomer compositions without aggregate or with very fine aggregate have been introduced as a means of densifying concrete structures. These aggregate-free compositions are applied to concretes and allowed to penetrate and fully polymerize within the voids and cracks of the concrete to provide a denser, more coherent concrete structure. Such compositions must contain oxygen deactivators (driers), polymerization catalysts and accelerators to assure complete curing of the applied composition.
Polyester polymer concrete compositions have not been looked upon favorably, especially for inside application because the primer compositions utilize organic materials of low flash point producing vapors which are disagreeable and sometimes toxic. In addition, the conventional primers for polyester polymer concretes are not effective when applied to damp or wet concrete substrates. Finally, conventional primers are effective only if the polymer concrete is applied immediately after application of the primer which is often difficult to do in field applications.
A method is desired which can enhance the use of polyester-based concrete overlay compositions by providing for damp and wet substrate application, long effective time between primer and polymer concrete application, enhanced bond strength between polyester concrete overlay and substrate and which does not produce noxious or toxic vapors.